1. Field of the Invention
The present invention relates to a method and system for automatically starting and stopping a vehicle engine during a non-driving period for the purpose of maintaining a comfortable temperature within the vehicle cabin.
2. Description of Prior Art
When the price of petroleum rises, the importance of reducing fuel consumption heightens proportionately for transportation and shipping businesses. That axiom is particularly true for businesses of the trucking industry, as fuel costs can be one of the largest business expenses that a trucking company incurs.
Of course, hauling heavily weighted cargo trailers is a reason for high fuel consumption. Another, and more avoidable, reason is prolonged engine idling during periods when freight trucks are not being driven. Often, a truck driver will idle the engine of his parked truck while he rests inside the cabin area of the vehicle. This engine idling allows operation of the air conditioning and heating system, powered by the vehicle's engine, to keep the cabin at a comfortable temperature. However, a significant amount of fuel may be consumed in the process. To wit, it is estimated that a typical diesel truck engine burns approximately one gallon of diesel fuel per hour of idling time. So, for some time, the trucking industry has recognized a particular need to develop ways of controlling cabin temperature of a non-moving vehicle in a fuel-efficient manner.
In addition to the general need for reducing the amount of fuel consumed by running an engine merely in order to maintain cabin comfort, there is the specific need to limit engine idling to conform with “anti-idling” laws that many states and local jurisdictions have enacted. These laws impose restrictions on engine idling for the purpose of controlling emissions. For example, the state of New York enacted a law prohibiting heavy-duty vehicles from idling more than five consecutive minutes, except under limited circumstances.
A way to limit, or avoid altogether, engine idling during non-driving periods is to use a generator-powered heating and cooling system. The generators, or “power packs”, used effectively eliminate the need to run the engine for the sole purpose of operating a heating and cooling system. However, there are negative aspects of using power packs. First, they may be too expensive for a freight company to equip its entire fleet with or for an independent truck operator on a limited fiscal budget. Second, for a variety of reasons, they may not be compatible with all vehicles. Third, they significantly increase the total weight of the vehicle, as power packs can weigh over 700 pounds. Consequently, while a power pack may increase a vehicle's overall fuel economy by reducing the need for engine idling during non-driving, it may actually reduce fuel economy during driving.
Another solution for reducing engine idling time, and a solution that the present invention embodies, is a method and system for monitoring air temperatures and controlling operation of the engine accordingly to maintain a comfortable cabin temperature during non-driving periods. For examples, U.S. Pat. No. 5,317,998 to Hanson, et al. discloses several versions of a method for automatically starting and stopping a truck engine in order to conserve fuel while controlling the truck cabin temperature, and U.S. Pat. No. 5,072,703 to Sutton discloses an apparatus for doing the same.
Nevertheless, it can be appreciated that there exists a need for an improved method of controlling a vehicle engine principally to maintain a comfortable cabin temperature during non-driving periods. More specifically, there is a need for one that starts the engine only when temperatures inside and outside the vehicle cabin are both above or both below a temperature range deemed acceptable by the vehicle operator. There is a secondary need for an engine control method in which the duration of each idling interval may be limited in accordance with the operator's pre-set instruction—an instruction that can be completely arbitrary or may be specifically necessary for compliance with applicable anti-idling law. It also can be appreciated that there is a need for such a method to contemplate use of a wide array of heating and cooling apparatuses, including those featuring automatic temperature control capability. The present invention substantially fulfills these needs.